Conventionally, various kinds of semiconductor devices are known. For instance, there exists a semiconductor device called an IPM (Intelligent Power Module). This type of semiconductor device includes semiconductor chips, die pads, a heat dissipation plate, a bonding layer and a sealing resin. The semiconductor chips are disposed on the die pads, respectively. The die pads are bonded to the heat dissipation plate via the bonding layer. The sealing resin covers the semiconductor chips, the die pads, the heat dissipation plate and the bonding layer. Such a semiconductor device called IPM is disclosed in e.g. Patent Document 1.
Conventionally, to manufacture a semiconductor device of this type, the die pads and the heat dissipation plate are bonded together before or at the same time as the sealing resin is formed. In bonding each die pad to a heat dissipation plate, the die pad is pressed against the heat dissipation plate by using a relatively thin pin. When only a portion of the die pad is pressed with a pin, the force is exerted only to the portion of the die pad, so that the die pad may tilt with respect to the heat dissipation plate. Further, when a pin is not used, the die pad may move in the process of forming the sealing resin, which may lead to problems such as cutting of the wires. To avoid such a problem, the die pad needs to be fixed with a pin. To prevent the die pad from tilting with respect to the heat dissipation plate, a plurality of portions of the die pad need to be pressed with pins. To press a plurality of portions of the die pad with pins, the die pad needs to have spaces for the pins, which hinders size reduction of the semiconductor device.
In the above-described semiconductor device, the distance between the die pads and the heat dissipation plate is set to a certain value. Positioning each of the die pads with respect to the heat dissipation plate so that the distance between the die pad and the heat dissipation plate is the predetermined value requires a high level of technique and is not easy.
Conventionally, various kinds of semiconductor devices are known. For instance, there exists a semiconductor device called an IPM (Intelligent Power Module). This type of semiconductor device includes semiconductor chips, die pads, terminals, a heat dissipation plate, a bonding layer and a sealing resin. The semiconductor chips are disposed on the die pads, respectively. The die pads are bonded to the heat dissipation plate via the bonding layer. The sealing resin covers the semiconductor chips, the die pads, the heat dissipation plate and the bonding layer. The terminals are connected to the die pads, respectively, and project from the sealing resin. The terminals are arranged in parallel to each other.
When the semiconductor device is used, a large potential difference is generated between the terminals. Further, it is necessary to prevent dielectric breakdown and the resulting current flow from occurring between adjacent terminals during the use of the semiconductor device. Thus, a high withstand voltage needs to be secured between adjacent terminals. For instance, in the semiconductor device disclosed in Patent Document 2, the withstand voltage between terminals is made high by fitting an insulating tube to each terminal. However, in the semiconductor device disclosed in Patent Document 1, the end of each terminal is not covered by an insulating tube. When the end of each terminal is not covered by the insulating tube, dielectric breakdown may occur in a space between the ends of the terminals and current may flow in the space. To prevent this, a considerably large distance needs to be secured between the ends of the terminals. This is not suitable for size reduction of the semiconductor device.
Conventionally, various kinds of semiconductor devices are known. For instance, there exists a semiconductor device called an IPM (Intelligent Power Module). This type of semiconductor device includes semiconductor chips, die pads, terminals, a heat dissipation plate, a bonding layer and a sealing resin. The semiconductor chips are disposed on the die pads, respectively. The die pads are bonded to the heat dissipation plate via the bonding layer. The sealing resin covers the semiconductor chips, the die pads, the heat dissipation plate and the bonding layer. The terminals are connected to the die pads, respectively, and project from the sealing resin. The terminals are arranged in parallel to each other. This type of semiconductor device is described in Patent Document 2.
In the state in which the semiconductor device is mounted, the heat dissipation plate of the semiconductor device is held in contact with a heat dissipating member having a high thermal conductivity. There is a demand for a technique for quickly transmitting the heat generated at the semiconductor chips of a semiconductor device to a heat dissipating member.
Conventionally, various kinds of semiconductor devices are known. An example of a semiconductor device is disclosed in Patent Document 3. The semiconductor device disclosed in this document includes semiconductor chips, a die pad and a molding resin. The semiconductor chips are disposed on the die pad. The molding resin covers the semiconductor chips and the die pad. In this semiconductor device, the semiconductor chips are disposed on a same surface of the die pad. Thus, the position of each semiconductor chip on the die pad is restricted by arrangement of other semiconductor chips. For instance, the semiconductor chips need to be arranged as spaced apart from each other by a certain distance as viewed in the thickness direction of the die pad. This type of semiconductor device has room for improvement in size reduction.
FIG. 95 shows an example of conventional semiconductor device (see e.g. Patent Document 4). The semiconductor device 900 illustrated in the figure includes a semiconductor element 904 mounted on an island 901 made of a metal. From the island 901A extends a lead 902. The semiconductor element 904 is connected to a lead 903 via a wire 905. The entireties of the semiconductor element 904 and the island 901 and part of each lead 902, 903 are covered by a sealing resin 906. The semiconductor device 900 is mounted on a non-illustrated circuit board and operates in accordance with the function of the semiconductor element 904.
In recent years, an IPM (Intelligent Power Module) has become widely used as a semiconductor device for converting inputted current into current of desired specifications and outputting the current. When the semiconductor device 900 is designed as an IPM, the semiconductor device incorporates, as a semiconductor element 904, a control element such as a power MOSFET or an IGBT (insulated gate bipolar transistor) and a driver element for driving and controlling the control element. Since the control element considerably heats up due to current flow, the heat dissipation performance of the semiconductor device 900 needs to be enhanced. Further, when the control element and the driver element are not properly arranged, the size of the semiconductor device 900 becomes large.
Conventionally, a semiconductor device in which a semiconductor element is resin-molded is widely used (see e.g. Patent Document 3). FIG. 123 shows an example of such a semiconductor device. The semiconductor device 90 shown in FIG. 123 includes a pair of terminal leads 91, 92, a semiconductor element 93, an insulating resin sheet 94, a metal member 95 made of a metal, wires 96, and a sealing resin 97 protecting these members. The terminal lead 91 is made by e.g. working a lead frame made of copper and includes a die pad 911. The semiconductor element 93 is mounted on the front surface of the die pad 911 and electrically connected to the terminal leads 91 and 92 via wires 96. The semiconductor element 93 is actuated by applying current to the terminal leads 91, 92. At that time, the semiconductor element 93 heats up. The metal member 95 is provided to efficiently dissipate heat generated by the semiconductor element 93 to the outside. The resin sheet 94 bonds the reverse surface of the die pad 911 and the front surface of the metal member 95. The resin sheet 94 is made of an epoxy resin containing a filler for enhancing the thermal conduction.
To bond the die pad 911 and the metal member 95 by using the resin sheet 94, pressing is performed in e.g. a hot environment. According to this manufacturing process, pressure is applied to the resin sheet 94 in the thickness direction. When the pressure application is uneven, the resin sheet 94 may be deformed into an undesired shape, as shown in FIG. 124. In the example shown in FIG. 124, the die pad 911 is also deformed to come into contact with the metal member 95 due to the pressure. Since the die pad 911 is electrically connected to the terminal lead 91, contact of the die pad 911 and the metal member 95 may result in the formation of an unintentional current path when the semiconductor device 90 is incorporated in a circuit.
Even when the situation shown in FIG. 124 does not occur, reduction of the thickness of the resin sheet 94 makes it difficult to maintain the insulation between the metal member 95 and the die pad 911, and the semiconductor device 90 may not be able to secure the withstand voltage. Further, the pressure may make the distribution of the filler in the resin sheet 94 uneven. In such a case, the heat dissipation performance of the resin sheet 94 may vary depending on positions.
In this way, although the provision of the metal member 95 is effective for enhancing the heat dissipation performance of the semiconductor device 90, it may degrade the reliability of the device.